Field of the Invention
The present invention relates to a plug-in hybrid electric vehicle (PHEV), and more particularly, to a method and apparatus for controlling a battery charge of a motor system of the PHEV.
Discussion of the Related Art
A plug-in hybrid electric vehicle (PHEV) may employ an electric motor in addition to an engine as a power source to reduce exhaust gas and enhance fuel efficiency. The PHEV may be driven in various different driving modes such as an electric vehicle (EV) mode that corresponds to a mode of a pure electric vehicle using power of a motor, a hybrid electric vehicle (HEV) mode in which a torque of a driving motor is used as auxiliary power while torque of an engine is used as main power, and a charging mode in which the vehicle may be driven while a battery is charged by converting mechanical energy of the engine into electric energy during driving.
In this way, the PHEV may supply power using electric energy of the battery together with mechanical energy of the engine as a power source, and generate electric energy from the motor during driving, and thus may enhance fuel efficiency of the vehicle and efficiently use energy. The PHEV includes a driving motor and a hybrid starter & generator (HSG) motor. The driving motor mainly delivers power to the vehicle, and the HSG motor mainly starts the engine and functions as a generator. Both motors may supply power to the PHEV together with the engine, and function as a generator configured to convert mechanical energy of the engine into electric energy.
Meanwhile, the PHEV using the driving motor may have an overheated motor, a temperature of which increases to more than a particular level, while the driving motor is driven or energy is generated from the driving motor. Specifically, the motor may be overheated due to heat loss that occurs in a process of generating electric energy from kinetic energy, and a temperature of the motor may increase due to driving and generation for a substantial period of time when the motor has a substantial heat value in comparison with cooling capacity.
When a temperature of the driving motor increases due to excessive generation, several problems may occur. For example, charging of the battery may be suspended due to an excessively high temperature of the driving motor during driving in the charging mode. In addition, even when the battery is sufficiently charged, the excessively high temperature of the motor may cause burning of a component and may affect operation of the motor. Thus, there may be a limit in driving the PHEV in the EV mode from the viewpoint of a system.